Where do the bubbles come from in sparkling wine and champagne?

‘Traditional’ method champagnes and sparkling wines have finer, longer lasting bubbles, but what gives these wines their fizz in the first place?

Not all bubbles are created equal. Wines made by the ‘traditional’ or ‘champagne’ method, tend to produce longer lasting, finer bubbles than those produced in other ways, such as the ‘charmat’ method: the other key way to make a wine sparkle. What though, are the other differences between the ‘champagne’ and the ‘charmat’ methods, how do the bubbles get in there in the first place and do the differences end up affecting the price and the taste?

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Fizz from fermentation

In the magic of winemaking, grape juice is turned into wine by the process of fermentation. The yeasts that occur naturally on the grape skin (or are sometimes added by a winemaker) start to eat the sugar in the juice, producing alcohol and CO2 as by-products. In still wine, this CO2 is simply allowed to dissipate. To make sparkling wine however, a still wine is made and then a second fermentation process happens only this time, the CO2 is prevented from dissipating, dissolving instead into the wine and creating bubbles. This alchemy is achieved by adding a sugary liquid with yeast (tirage) to a still ‘base’ wine in order to kick off the second fermentation. The crown cap means the gas can’t escape so it dissolves into the wine and hey presto – bubbles.

Champenoise vs Charmat

Many sparkling wines are not trying to mimic the champagne style, but instead are made for earlier, simpler drinking. Introducing the ‘tank’ or ‘charmat’ method, used to produce the likes of Prosecco and Lambrusco: sparkling, frothy wines with largeish bubbles that are made to be drunk young. With charmat, the base wine is made as normal, but the secondary fermentation happens in a large tank once the ‘tirage’ has been added rather than single bottles. Once completed, the bubbly wine is filtered under pressure and bottled, then sold without any significant ageing. It’s a quick and relatively inexpensive method.

On the other side of the sparkling wine scale, ‘traditional method’ fizz such as champagne, cava and wineries such as Chandon or Cloudy Bay for Pelorus, undergo a lengthier, more fiddly process, where the bubbles are created in each individual bottle rather than large tanks. The base wine is poured into bottles with a small amount of ‘tirage’ liquid and sealed tightly with a crown cap to ferment and get bubbly. Depending on the style, a wine might sit on the dead yeast cells (lees) in the bottle for a few months (a minimum of 15 months in Champagne) or even years before the lees is removed by ‘disgorging’. This long maturation period allows the bubbles to blend harmoniously. The bottle is then topped up with base wine with a sweetness level according to the final style desired.

For these traditional method sparkling wines, the flavours are more complex than with the ‘charmat’ wines; the mousse tends to be creamier too and the bubbles much finer, lasting longer. When you compare these to sparkling wines made in bulk that don’t need ageing or disgorging and consider the fact that they often use more valuable, ‘finer’ grapes, it becomes clear why they also need to be quite a bit more expensive.